1. Field of the Invention
The present invention relates generally to a web roll wrapping apparatus for wrapping a web roll in a sheet, and more particularly to a web roll wrapping apparatus for wrapping a roll of photosensitive web such as printing paper and photographic film (e.g. one in Japanese Utility Model Publication No. 1-38582) in a light-shielding sheet.
2. Description of Related Art
A photosensitive web is rolled and wrapped in a light-shielding sheet in a darkroom. The light-shielding sheet is wider than the roll of the photosensitive web, and is coated with a thermoplastic adhesive. The light-shielding sheet is wound at least once around the outer peripheral surface of the web roll, and protruding parts of the wound sheet, which parts protrude from both end faces of the web roll, are folded down at a right angle onto the end faces of the web roll. Then, the folded parts of the sheet are heat-sealed with the thermoplastic adhesive. Thus, the web roll is wrapped in the light-shielding sheet.
Japanese Patent Provisional Publication No. 63-168767 discloses an example of a conventional web roll wrapping apparatus which comprises a mechanism for holding and rotating the web roll, and folding members for folding and heat-sealing the protruding parts of the wound sheet. The wrapping apparatus rotates the web roll around its core with the holding mechanism, and moves the folding members, which are arranged at both ends of the web roll, back and forth in the diametrical direction of the web roll. Thereby, the protruding parts of the wound sheet are folded and heat-sealed by the folding members.
In the conventional wrapping apparatus, each folding member has both functions of folding and heating the protruding part of the wound sheet, and thus, it is difficult to position a heating means (a heater) on the folding member. For example, if the position of the heater on the folding member shifts toward the tip of the folding member, the end face of the web roll is harmfully heated, thereby damaging the photosensitive web.
Moreover, the conventional wrapping apparatus moves the folding members back and forth in the diametrical direction of the web roll. Thus, there is a disadvantage that an electric wire connected to the heater on the folding member may be broken.